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Odlaganje mešanih komunalnih odpadkov (MKO) predstavlja v svetovnem merilu še vedno pomembno metodo ravnanja z odpadki. Transfer sodobnih tehnologij odlaganja iz razvitih v nerazvite dežele se pogosto ni obnesel zaradi nesprejemljivo visokih stroškov, povezanih z izgradnjo in obratovanjem sodobno grajenih odlagališč. Posledično, znaten del odpadkov v soc-ekonomsko najranljivejših delih sveta še vedno konča svojo pot na disperznih deponijah, ogrožajoč vodonosnike in druge segmente tamkajšnjega okolja. Po drugi strani je že desetletja znano, da so se male, slabo skompaktirane in slabo tesnjene medobčinske nadzemne deponije obratujoče v 70-ih in 80-ih letih prejšnjega stoletja v splošnem relativno hitro stabilizirale in okolja kasneje niso več ogrožale, kar za moderno grajena odlagališča suhega tipa ne velja. V kontekstu tega spoznanja smo v obdobju 2002 – 2020 na pilotnem raziskovalnem odlagališču pri Ajdovščini ob rednem obratovanju enote v okviru komunalnega podjetja izvajali tudi aplikativne raziskave na temo koriščenja hipotetičnih ekonomskih in okoljevarstvenih prednosti odlaganja odpadkov v nadzemnih deponijah nizke gostote. Zasnovan je bil poseben tip nizko-stroškovnega komunalnega odlagališča, imenovan ''visoko-prepustna trajnostna deponija'' (VPTD). Podobno kot velja za do neke mere sorodno, ''Fukuoka''- metodo odlaganja MKO, predstavlja pasivna aeracija najpomembnejši okoljevarstveni proces, ki se na tovrstnem objektu oz. napravi odvija. Ker meritve intenzivnosti infiltracije zraka v telo odlagališča v praksi niso izvedljive, se je letno pretočene količine kisika ocenilo z izračuni, upoštevajoč zakonitosti relevantnih gonilnih mehanizmov. Rezultati izvedenih meritev na pilotnem odlagališču so potrdili pričakovanja, da je generacija karakterističnih vodnih onesnažil ter metana na enoto odloženega odpadka v primerjavi s konvencionalnimi odlagališči znatno manjša, razpolovna doba odvijanja stabilizacijskih procesov pa znatno krajša. Posledično, koncentracijo onesnažil v saturirani coni na dnu odlagališča je možno zmanjšati do neškodljivih ravni desetletja prej kot lahko pride do njihovega preboja na drugo stran ustrezno dimenzionirane glinene bariere. Zaradi hitrega poteka stabilizacijskih procesov lahko upravljavec degradirani prostor zaprtih delov odlagališča takoj nameni izvajanju komplementarnih dejavnosti z odpadki. Z izvedbo komparativnih analiz dolgoročnega okoljevarstvenega tveganja smo demonstrirali, da je okoljevarstvena učinkovitost odlagališča tipa VPTD kljub njegovi nizko-stroškovni naravi primerljiva z moderno grajenimi odlagališči bioreaktorskega tipa. Conventional landfilling of municipal solid waste (MSW) appears to be a widely accepted waste management method still in use today in many parts of the world. The state of the art waste disposal technologies did not take root in low income countries because of the related high costs. Consequently, considerable part of disposed of waste ends up in poorly controled landfills and dumps, posing potential threats to the adjacent aquifers. However, it has been known for decades that old, unlined, loosely compacted, small MSW landfills which were active in developed countries during the 70's and 80's generaly stabilised quickly after closure and posed little if any threat to the environment afterwards, which is not the case with highly engineered, dry entombment landfills. In this context, applied research has been carried out at one pilot-scale waste disposal site in the Vipava valley, Slovenia, during the period between 2002 and 2020 in order to explore the supposed environmental and economic benefits of landfilling MSW in above-ground, low-density deposits. A new type of low-cost, semiaerobic landfill was developed, called ''high- permeability landraise'' (HPL). As is the case with somewhat similar Fukuoka type of landfill, passive aeration is designed to be the main driving process to accelerate waste stabilisation. Since no reliable methods for measuring air fluxes into the landfill existed, alternative calculations were performed instead considering all the relevant mechanisms involved. Monitoring results from the pilot landfill were compared to monitoring results derived from landfills of different types. It was confirmed that concentration of pollutants within the primary leachate and methane to CO2 generation ratios within the landfill gas characteristic for HPL were much smaller when compared to those characteristic for modern, dry-type landfills of the same age. Also, waste stabilisation half-life appeared to be much shorter. In this way, pollutant concentrations at the bottom of the landfill can be reduced to unharmful levels decades before the pollutants manage to penetrate the designed clayey liner and break through. The ability to promptly stabilise closed landfill cells can have profound positive effects not only on the long-term management of environmental risks, but also on long-term developmental opportunities of the site. Quantitative comparative analysis performing long-term risk assessments demonstrated HPL performs on a par with modern bioreactor landfills in terms of environmental safety despite the low cost of such kind of facility. |
